The commission disqualified former air force commander Ahmed Shafik, who was appointed prime minister last year in the waning days of Hosni Mubarak’s presidency. A new law bars former Mubarak officials who had served in the past 10 years from seeking office.

• Amr Moussa, the former foreign minister and Arab League secretary-general.

• Abdel Moneim Aboul Fotouh, a longtime Brotherhood leader who was expelled from the group last year for defying its promise at the time not to field a presidential candidate.

The Brotherhood reversed its stance late last month, citing threats to democracy from the ruling military council. Mr. Morsi has called for strict clerical oversight of Egyptian law.

Egyptians will vote in the election’s first round May 23 and 24, and the two top vote-getters will compete in a runoff June 16 and 17 in the likely event that no candidate gets a first-round majority.

The winner could decide the fate of Egypt’s year-old revolution, which already has taken a decidedly Islamist turn. The Brotherhood’s Freedom and Justice Party and the Salafist Nour Party won a combined two-thirds of the vote in parliamentary elections.

Given that Mr. Shafik had been lagging in the polls, analysts said it is too early to know how his disqualification would affect the election’s outcome.

“I’m not sure it affects the race all that much,” said Steven Cook, senior fellow at the Council on Foreign Relations and author of “The Struggle for Egypt.”

Mr. Moussa - once considered the overwhelming favorite - faces an uphill battle, even if he makes the runoff. A recent poll showed that 57 percent of Egyptians prefer an Islamist candidate.

“The key question is whether Egyptian secularists turn out in sufficient numbers in support of Amr Moussa … and whether the Islamists unite around one candidate or split their vote between Morsi and Aboul Fotouh,” said Eric Trager, an Egypt expert at the Washington Institute for Near East Policy.

About the Author

Ben Birnbaum is a reporter covering foreign affairs for The Washington Times. Prior to joining The Times, Birnbaum worked as a reporter-researcher at the New Republic. A Boston-area native, he graduated magna cum laude from Cornell University with a degree in government and psychology. He won multiple collegiate journalism awards for his articles and columns in the Cornell Daily Sun.